Patent GB-843406-A (GB)
Title: Improvements relating to signal-translating apparatus
Inventor: WILLIAMSON DAVID THEODORE NELS
IPC: H03M1/00
Filed: 1956-11-27
Abstract: 843,406. Programmed electric control systems. FERRANTI Ltd. Nov. 26, 1957 [Nov. 28, 1956], No. 36190/56. Class 38 (6). Signal-translating apparatus for receiving information in the form of a train of electrical input pulses some of positive sense and some of negative sense and for converting that information to the form of a control sinusoidal signal phase-modulated with respect to a reference sinusoidal signal includes a generator of electric pulses of constant sense and constant repetition frequency, means for deriving from the generator pulses a reference sinusoidal signal such that the number of generator pulses which are received during each half-cycle of the signal has a constant value, a combining stage for interlacing the generator pulses with said input pulses to produce a combined train of pulses, and means for deriving from said combined train of pulses said control signal such that the algebraic sum of the pulses of the combined train which are received during each half cycle of the control signal has said constant value. Two signaltranslating devices are described, the first, Fig. 1, for receiving information in the form of a train of electrical input pulses some of positive sense and some of negative sense and converting that information to the form of a control sinusoidal signal phase-modulated with respect to a reference sinusoidal signal and the second, Fig. 2, for performing the inverse translation. The devices are said to be of use in machine tool control equipment where each positive pulse represents an increment of movement in one direction and each negative pulse an increment in the other direction. In the first translator, Fig. 1, a stream of regularly occurring reference pulses produced by a pulse generator 11 pass through a combined counter and squarewave generator 12 and a filter circuit 13 to produce, on a lead 14, a reference sinusoidal signal each complete cycle of which corresponds to a fixed number N of pulses from the generator 11. The reference pulses are also applied, together with the incoming information pulses on a lead 16, via an interlacer 15 which mixes the pulses in such a way that no two coincide with each other, to an algebraic counter and squarewave generator 17 and then to a filter circuit 18, the algebraic counter producing a square wave for every net ¢N positive pulses received, so that the final result is a sinusoidal output signal on a lead 19 phase-modulated with respect to the reference signal by the incoming information pulses. In the inverse translator, Fig. 2, the reference sinusoidal signal is applied on a lead 23 to a discriminator 24 which (being in a feedback loop 21, 22) controls a blocking oscillator 21 so that it produces N pulses for each complete cycle of the reference signal, the phasemodulated information signal is applied on a lead 28 to a discriminator which controls a second blocking oscillator 25 so that it produces N pulses for each complete cycle of the information signal, and the pulse signal, representing the incoming information appears on a lead 30. The two blocking oscillators are interlinked, as shown, so that they cannot produce pulses simultaneously, and the pulses they produce pass on leads A and B to a gating circuit 31 arranged to produce no output on leads C and D if it receives pulses alternately on leads A and B or to produce a pulse on lead C or D respectively if two consecutive pulses arrive on leads A or B. The pulses so produced are combined in a further stage 32 to produce the required output signal. The output signals from either of the two translating devices may be recorded for example on magnetic tape.